The present invention relates to a folding tool for automatic roll folding, and comprises a first member fixed to a manipulator, a second member movably connected to the first member and including a first folding roller, and a spring disposed to permit a relative movement between the first member and the second member, under the action of a force increased by the movement.
The present invention also relates to a method of roll folding by means of a folding tool which comprises a fixed first member at a manipulator and a second member movably connected to the first part and having a folding roller, the member being urged away from the first member by a spring force directed away from the first member.
Finally, the present invention also relates to the use of the above-outlined folding tool and the reduction into practice of the above-outlined method.
In the joining together of two sheet metal parts in such contexts where the requirements on surface finish are high, folding is often employed as a better alternative to welding. The folding process is such that one of the workpieces is given an edge portion projecting out over the second workpiece, the edge portion being folded in over the second workpiece and urged against it such that the edge of the second workpiece will be accommodated between the first workpiece and its folded-over edge portion. For the above-mentioned folding over of the edge portion of the first workpiece, use is generally made of a roller which is displaced in the longitudinal direction of the edge portion.
EP 577 876 discloses a folding apparatus mounted on an industrial robot. The apparatus described in this publication has a first guide member which is immovably secured in the movement devices of the robot, and a second guide member which is accommodated in and displaceably guided in a recess in the first guide member. The two guide members thereby together form a telescope arrangement. Between the two mutually movable guide members, a spring is disposed which affects the movements between the guide members and is directed to counteract movement of the guide members towards one another. The above-described construction makes for the movement of the folding roller from and towards the movement devices of the robot which is necessary for an adequate folding result. However, the precision in the movements of the folding roller is far too poor because of the selected formation of the guide.
In the above-outlined construction, the folding roller is also located a considerable distance laterally outside the longitudinal direction of the telescope arrangement, which coincides with the direction of movement of the second guide member. Hereby, the guide member will be obliquely loaded so that a xe2x80x9cjammed drawer effectxe2x80x9d may be feared. Such an oblique loading destroys the precision in the movements, since the smallest play in the telescopic guide because of the large lateral projection of the folding roller gives large movements in the folding roller. In addition, a considerably harder wear on the mutually movable components may be feared than would otherwise be the case.
The prior art apparatus has only a single folding roller, for which reason time-consuming readjustment work or retooling will be the result.
The present invention has for its object to design the folding tool intimated by way of introduction such that it obviates the drawbacks inherent in prior art technology. In particular, the present invention has for its object to design the folding tool in such a manner that the folding roller will have a guiding with considerably higher precision than that which can be achieved employed prior art technology. Further, the present invention has for its object to realise a folding tool which is not subjected to oblique loadings which may destroy the service life or affect the movement pattern of the folding roller. Finally, the present invention also has for its object to realise a folding tool which is extremely robust and operationally reliable when in use.
The objects forming the basis of the present invention will be attained if the folding tool intimated by way of introduction is characterized in that the second member is rotatably connected to the first member.
In that the second member with the folding roller in principle executes a pendulum motion, its guiding can be made with considerably greater precision than is the case in a telescope arrangement with a folding roller projecting considerably in the lateral direction. Further, tendencies for oblique loading will be eliminated or reduced as a result of this construction.
Another object of the present invention is further to improve the precision of the folding tool.
According to the present invention, this is attained in that the folding tool includes a support roller and a plane roller, the support roller having a diameter which is greater than that of the plane roller, and the rollers being disposed to freely rotate about the same axis.
As a result of these features, the advantage will be afforded that the precision of the folding will not only be dependent on the accuracy of the movement pattern of the manipulator and the precision of the folding tool, but may be further improved by the abutment of the support roller against the workpiece or that surface on which it rests.
A further improvement of the precision of the folding, in particular in the lateral direction (sideways) will be achieved if a guide roller is employed during the final compression of the union, the so-called final folding. This guide roller is disposed to abut against a guide path which may be an integral part of the bed on which the workpiece rests. The axes of the guide roller and the folding roller intersect one another substantially at a right angle. As a result, the abutment pressure of each respective roller can be adjusted independently. It is thus possible to affect the abutment pressure of the folding roller against the workpiece without actuation.
Furthermore, the present invention has for its object to improve the flexibility and production capacity of the apparatus according to the present invention.
This object is attained if the folding tool includes a second folding roller which is rotary about an axis separate from the axis of the first roller.
As a result of these features, the advantage will be afforded that the folding tool need only be given new orientation in relation to the workpiece before a new working phase is commenced.
Finally, the present invention has for its object to realise the possibility of varying the spring constant in the spring which is included in the folding tool.
This object is attained in that the spring comprises a gas spring which has an expandable bellows containing a gas.
As a result, the possibility will be afforded of rapidly varying the force with which the folding tool abuts against the workpiece.